Derive class identity from one hierarchy graph

instance?, extend-protocol dispatch, isa?/supers/ancestors, and the exception
hierarchy each read their own hand-kept table, and those tables had drifted:
(instance? clojure.lang.Associative [1 2]) was true but a protocol extended to
Associative wouldn't dispatch to a vector; keyword/IFn and seq/Seqable had the
same split; (isa? ExceptionInfo RuntimeException) was false and
(supers NumberFormatException) was empty.

Add one FQN -> direct-supers graph (class-hierarchy.ss) and derive the views
from it. value-host-tags builds on the graph closure so a vector reports
Associative/Indexed/ILookup/Counted/Seqable, a keyword reports IFn, a seq
reports Seqable/List/Counted, etc. instance? now tests membership in that same
list, so it can't disagree with dispatch. canonical-host-tag recognizes any
modeled class (was a separate literal set missing Seqable/ILookup/...).
class-direct-supers unions the graph edges and class-supers returns the
transitive closure, so the exception hierarchy answers isa?/supers/ancestors.

The graph is open: jolt.host/register-class-supers! lets a library graft its
own classes on and get every view for free.

Runtime only, no re-mint. make test green (0 new/stale divergences), +3
JVM-certified corpus rows.

host/chez/rt.ss

@@ -356,6 +356,11 @@
 ;; jolt-pr-str (above), and the var-cell machinery — so loaded last.
 (load "host/chez/multimethods.ss")
 
+;; the single JVM class/interface graph — value-host-tags, instance?, isa?/supers,
+;; and the exception hierarchy all derive from it. Before records.ss so
+;; value-host-tags can build on jch-tags.
+(load "host/chez/java/class-hierarchy.ss")
+
 ;; records + protocols: defrecord/deftype/defprotocol/
 ;; extend-type/reify. A jrec record type set!-extended into the collection
 ;; dispatchers + a protocol registry. After multimethods.ss (chez-current-ns) and